F/T Transducer Without Electronics (TWE) ManualEngineered Products for Robotic Productivity Pinnacle Park • 1031 Goodworth Drive • Apex, NC 27539 • Tel: +1-919.772.0115 • Fax:

Engineered Products for Robotic ProductivityPinnacle Park • 1031 Goodworth Drive • Apex, NC 27539 • Tel: +1-919.772.0115 • Fax: +1-919.772.8259 • www.ati-ia.com

F/T Transducer Without Electronics (TWE)

Manual

Document #: 9620-05-TWE

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Manual, FT Sensor, TWEDocument #9620-05-TWE-16

Pinnacle Park • 1031 Goodworth Drive • Apex, NC 27539, USA • Tel: +1.919.772.0115 • Fax: +1.919.772.8259 • www.ati-ia.com2

ForewordInformation contained in this document is the property of ATI Industrial Automation, Inc. (ATI) and shall not be reproduced in whole or in part without prior written approval of ATI Industrial Automation, Inc. The information herein is subject to change without notice and should not be construed as a commitment on ATI Industrial Automation, Inc. This manual is periodically revised to reflect and incorporate changes made to the F/T system.

ATI Industrial Automation, Inc. assumes no responsibility for any errors or omissions in this document.

Copyright © (2020) by ATI Industrial Automation, Inc., Apex, North Carolina USA. All Rights Reserved. Published in the USA.

In consideration that ATI Industrial Automation, Inc. (ATI) products are intended for use with robotic and/or automated machines, ATI does not recommend the use of its products for applications wherein failure or malfunction of an ATI component or system threatens life or makes injury probable. Anyone who uses or incorporates ATI components within any potentially life threatening system must obtain ATI’s prior consent based upon assurance to ATI that a malfunction of ATI’s component does not pose direct or indirect threat of injury or death, and (even if such consent is given) shall indemnify ATI from any claim, loss, liability, and related expenses arising from any injury or death resulting from use of ATI components.

All trademarks belong to their respective owners. Windows is registered trademarks of Microsoft Corporation.

Electromagnetic Compatibility

This device complies with Part 15 of the FCC Rules, Class A. Operation is subject to the following two conditions: (1) this device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.

This device complies with EMC Directive 2004/108/EC and conforms to the following standards: EN55022:1998+A1:2000 +A2:2003, EN61000-4-2:1995 +A1:1998+A2:2001, EN61000-4-3:2002, EN61000-4-4:2004, EN61000-4-5:1995 +A1:1996, EN61000-4-6:1996 +A1:2001, EN61000-4-8:1995, EN61000-4-11:2001.

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Note:

Please read the manual before calling customer service. Before calling, have the following information available:

1. Serial number (e.g., FT01234)

2. Transducer model (e.g., Nano17, Gamma, Theta, etc.)

3. Calibration (e.g., US-15-50, SI-65-6, etc.)

4. Accurate and complete description of the question or problem

5. Computer and software information. Operating system, computer type, drivers, application software, and other relevant information about your configuration.

If possible, be near the F/T system when calling.

Please contact an ATI representative for assistance, if needed:

Sale, Service and Information about ATI products:

ATI Industrial Automation 1031 Goodworth Drive Apex, NC 27539 USA www.ati-ia.com Tel: +1.919.772.0115 Fax: +1.919.772.8259

Application Engineering Tel: +1.919.772.0115, Extension 511 Fax: +1.919.772.8259 E-mail: [email protected]



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Table of Contents1. Safety ......................................................................................................................................... 7

1.1 Explanation of Notifications ......................................................................................................... 7

1.2 General Safety Guidelines ............................................................................................................ 8

1.3 Safety Precautions ........................................................................................................................ 8

2. System Overview ...................................................................................................................... 92.1 System with Transducer, Customer Electronics, and DAQ Device .......................................... 9

2.2 Interface Plates ............................................................................................................................ 10

2.3 Transducer ................................................................................................................................... 10

2.4 Transducer Cable ........................................................................................................................ 10

2.5 TWE Calibration Spreadsheet Overview ................................................................................... 11

3. Electrical Setup ...................................................................................................................... 123.1 Excitation Voltage Supply and Six Amplifiers .......................................................................... 13

3.1.1 Excitation Voltage Supply ................................................................................................. 13

3.1.2 Six Amplifiers .................................................................................................................... 14

3.1.3 DAQ System ..................................................................................................................... 15

3.1.4 Computer .......................................................................................................................... 15

3.1.5 Connections (cables and connectors) .............................................................................. 15

3.2 TWE Calibration Spreadsheet (FTxxxxx TWE.xlsx) ................................................................. 153.2.1 Worksheet 1. Overview ................................................................................................... 163.2.2 Worksheet 2. Electrical Setup ........................................................................................ 173.2.3 Worksheet 3. System Characterization ......................................................................... 183.2.4 Worksheet 4. Sample Calculations ................................................................................ 203.2.5 Worksheet Gain Worksheet ............................................................................................ 21

3.3 How to Use the TWE Calibration Spreadsheet ......................................................................... 22

4. Periodic Maintenance ............................................................................................................ 234.1 Inspection of Cables ................................................................................................................... 23

4.2 Calibration .................................................................................................................................... 23

5. Troubleshooting ..................................................................................................................... 246. Appendix ................................................................................................................................. 25

6.1 Appendix A—Transducer Cable Connectors and Signals....................................................... 256.1.1 Transducer Mating Connectors ........................................................................................ 25

6.1.2 Pin Connections on the Cable Connectors ...................................................................... 256.1.2.1 Nano/Mini Integral Cable Connectors ............................................................... 256.1.2.2 9105-C-x-A Cable Connectors .......................................................................... 26


Manual, FT Sensor, Axia80 Universal Robot (URDocument #9620-05-TWE-16


6.2 Appendix B—Amplification and Excitation .............................................................................. 276.2.1 Examples .......................................................................................................................... 27

6.3 Appendix C—Mechanical and Electrical Overview of the Transducer ................................... 296.3.1 Mechanical Description .................................................................................................... 29

6.3.2 Electrical Description ........................................................................................................ 30

6.4 Appendix D—Resolution ............................................................................................................ 31

6.5 Appendix E—Detecting Sensitivity Changes ........................................................................... 31

6.6 Appendix F—Buffer Circuit ........................................................................................................ 31

7. Terms and Conditions of Sale ............................................................................................... 32




Glossary of TermsTerm DefinitionAccuracy See Measurement Uncertainty.Bit/Byte A unit of computer data.

Calibration The act of measuring a transducer’s raw response to loads and creating data used in converting the response to forces and torques.

Calibration Certificate

A statement that certifies the equipment measures correctly. These statements mean the equipment has been tested against national standards. The statements are produced as a result of calibration or re-calibration.

Compound Loading Any load that is not purely in one axis.Force The push or pull exerted on an object.F/T Force/Torque.F/T Transducer The device that converts force and torque into an electrical signal. Fxy The resultant force vector comprised of components Fx and Fy.

Hysteresis A source of measurement error caused by the residual effects of previously applied loads.

IPIngress Protection is a rating code per IEC standard. The rating classifies the extent to which a device is protected from outside extremities.

MAP Mounting Adapter Plate. The MAP part of the transducer is attached to the fixed surface or robot arm.

Maximum Single-Axis Overload The largest amount of load in a single axis (all other axes are unloaded) that the transducer can withstand without damage.

Measurement Uncertainty The maximum expected error in measurements, as specified on the calibration certificate.

Overload The condition where more load is applied to the transducer than the transducer can measure. Overload results in saturation.

QuantizationThe way the continuously variable transducer signal is converted into discrete digital values. Usually used when describing the change from one digital value to the next.

Resolution The smallest change in load that can be measured. This is usually much smaller than accuracy.

Saturation The condition where the transducer has a load or signal outside its sensing range.

Sensor The complete system that includes a transducer, cabling, and external electronics.

SG Strain Gage

TAP Tool Adapter Plate. The TAP part of the transducer attaches to the load that is to be measured.

TWE Transducer Without Electronics. An F/T transducer for advanced users who need to bypass standard ATI Industrial Automation electronics.

TWL A TWE F/T transducer with environmental connector. See TWE.Torque The measurement of a rotational force exerted on an object.

Transducer The electro-mechanical component that is placed in-line with the load to be measured.

Txy The resultant torque vector comprised of components Tx and Ty.


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1. SafetyThe safety section describes general safety guidelines to be followed with this product, explanations of the notifications found in this manual, and safety precautions that apply to the product. More specific notifications are imbedded within the sections of the manual where they apply.

1.1 Explanation of NotificationsThe following notifications are specific to the product(s) covered by this manual. It is expected that the user heed all notifications from the robot manufacturer and/or the manufacturers of other components used in the installation.

DANGER: Notification of information or instructions that if not followed will result in death or serious injury. The notification provides information about the nature of the hazardous situation, the consequences of not avoiding the hazard, and the method for avoiding the situation.

WARNING: Notification of information or instructions that if not followed could result in death or serious injury. The notification provides information about the nature of the hazardous situation, the consequences of not avoiding the hazard, and the method for avoiding the situation.

CAUTION: Notification of information or instructions that if not followed could result in moderate injury or will cause damage to equipment. The notification provides information about the nature of the hazardous situation, the consequences of not avoiding the hazard, and the method for avoiding the situation.

NOTICE: Notification of specific information or instructions about maintaining, operating, installing, or setting up the product that if not followed could result in damage to equipment. The notification can emphasize, but is not limited to: best operating practices and maintenance tips.




1.2 General Safety GuidelinesThe customer should verify that the transducer selected is rated for maximum loads and torques expected during operation. Because static forces are less than the dynamic forces from the acceleration or deceleration of the robot, be aware of the dynamic loads caused by the robot.

1.3 Safety PrecautionsWARNING: Performing maintenance or repair on the sensor, while circuits such as power are energized, could result in serious injury. Discharge and verify all energized circuits are de-energized in accordance with the customer’s safety practices and policies.

CAUTION: Modifying or disassembly of the sensor could cause damage and void the warranty. Use the supplied mounting adapter plate (MAP) and the provided tool side mounting bolt pattern to mount the sensor to the robot and customer tooling to the sensor. For more information, refer to Section 7—Terms and Conditions of Sale.

CAUTION: Using fasteners that exceed the customer interface depth penetrates the body of the sensor, damages the electronics, and voids the warranty. For more information, refer to Section 7—Terms and Conditions of Sale for more information.

CAUTION: Do not remove any fasteners or disassemble transducers, without a removable mounting adapter plate. Doing so can cause irreparable damage to the transducer and void the warranty. Leave all fasteners in place and the transducer in its assembled state. This applies to Nano, IP-rate, and some Omega transducers.

CAUTION: Probing openings in the transducer causes damage to the instrumentation. Avoid prying into openings of the transducer.

CAUTION: Do not exert excessive force on the transducer. The transducer is a sensitive instrument and can be damaged by applying a force that exceeds any of the single-axis overload values of the transducer, causing irreparable damage. Small Nano and Mini transducers can easily be overloaded during installation. For specific transducer overload values, refer to the F/T transducer manual, 9620-05-Transducer Section.


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2. System OverviewThe Transducer Without Electronics (TWE) Force/Torque (F/T) is a multi-axis force and torque detection system that simultaneously measures forces (Fx, Fy, and Fz) and torques (Tx, Ty, and Tz). TWE systems require the user to amplify and digitize the transducer signals. The user converts the digitized signals into force and torque values through a factory supplied calibration matrix.

This manual uses the term TWE to refer to both TWE and TWL F/T transducers.

2.1 System with Transducer, Customer Electronics, and DAQ DeviceFigure 2.1—A TWE System

User DAQ System

Amplified VoltagesLow-Level Voltages

ExcitationVoltage

DigitizedVoltages

User Computer

DAQ card drivers receive transducerload information.

User software uses the transducercalibration data to convert transducerload information into useable F/T data.

Transducer with TWE Calibration

User Amplified and Excitation Supply

g0, g1, g2, g3, g4, g5 G0, G1, G2, G3, G4, G5

A TWE system usually consists of the following:• TW, TWE, or TWL transducer with TWE calibration

• transducer cable

• interface plates for larger transducers (optional)

• spreadsheet with calibration information (sent to the user from ATI via e-mail, refer to Section 2.5—TWE Calibration Spreadsheet Overview)

• excitation voltage and six amplifiers with adjustable gain (user-supplied)

• data acquisition (DAQ) system for converting analog data into numerical values (user-supplied)

• computer and software (user-supplied)

• cables and connectors to connect the components (user-supplied)To convert raw voltages into F/T values a user can perform the necessary mathematical operations either with the supplied spreadsheet or a (user-supplied) custom software application.

CAUTION: The F/T sensor and the calibration matrix provided with it have been assigned matching serial numbers when the transducer was calibrated. If these serial numbers assigned to the F/T system do not match, the F/T output data will be incorrect.




CAUTION: For larger transducers (Gamma transducers and larger) with a removable MAP, do not touch any exposed instrumentation when the MAP is removed.

Exposed Instrumentation

Connector

2.2 Interface PlatesLarger transducers come with a standard mounting interface plate to mechanically attach the transducer to the apparatus that applies the force. Gamma, Delta, Theta, and Omega160 transducers also have a standard tool interface plate with an ISO 9409-1 interface for attaching to the customer tool.The plate consists of a plate and mounting fasteners. For more information, refer to the installation section and drawings in the F/T transducer manual, 9620-05-Transducer Section.

CAUTION: Cables and interface plates on the Nano and Mini transducers are permanently attached to the transducer and cannot be disconnected. Do not attempt to disassemble these transducers as damage will occur.

2.3 TransducerThe ATI TWE transducer is a compact, monolithic structure that converts force and torque into analog strain gage signals. Figure 2.2 shows the transducer with a standard tool adapter.For more information, refer to the installation section and drawings in the F/T transducer manual, 9620-05-Transducer Section.

Figure 2.2—Transducer

Transducer Connector

Mounting Adapter Plate (MAP)

Tool Adapter Plate (TAP)

Large Transducer with TWE calibration

Tool Adapter Plate (TAP)

Mounting Adapter Plate (MAP)

Integral Cable

Small Transducer withTWE calibration

2.4 Transducer CableThe high-flex transducer cable is electrically shielded to protect transmission of transducer data. The cables used in the Nano and Mini models are integrated into the unit. Other models use detachable cables. For information regarding the transducer’s electrical connections, refer to Appendix A—Transducer Cable Connectors and Signals.






2.5 TWE Calibration Spreadsheet OverviewUpon shipment of the TWE, ATI sends to the user via e-mail a spreadsheet with calibration information. This information is needed for the user’s system or computer to convert the transducer readings into a usable F/T output.To maximize accuracy, each transducer, sent to a user, is individually calibrated. Included with the transducer is a Microsoft® Excel® document named: FTxxxxx TWE.xlsx, where FTxxxxx is the transducer’s serial number. The calibration information specific to the transducer is included within the spreadsheet.This spreadsheet assists the user with the design of a signal conditioning system by calculating the gains and hardware bias offsets to optimize the system’s range and resolution. Within the spreadsheet are sample calculations for converting voltages into forces and torques. The worksheets within this spreadsheet provide the following functions:• an overview of the spreadsheet contents

• instructions for how to construct a system

• a place for users to record key properties of the system

• calculate F/T values read by the transducer

• assist the user to calculate the electrical gain of the user-supplied amplifiers.For additional information to assist with the setup and use of this spreadsheet, refer to Section 3.2—TWE Calibration Spreadsheet (FTxxxxx TWE.xlsx).




3. Electrical SetupThis setup guide details how to connect a TWE transducer to a user’s DAQ system. In Section 6—Appendix, additional information such as the transducer cable connectors and signals and advanced topics such as amplification/excitation, resolution, and detecting sensitivity changes are covered in detail. A system includes the components in the following table:

Table 3.1—Components of a TWE SystemComponent DescriptionTransducer with TWE Calibration An ATI transducer supplied with TWE calibration

Excitation Supply (user-supplied) Excitation voltage supply to power the ATI transducer’s strain gages (refer to Section 3.1.1—Excitation Voltage Supply).

Amplifiers (user-supplied) Amplifiers for each of the six ATI transducer low-level outputs (refer to Section 3.1.2—Six Amplifiers).

DAQ System (user-supplied) A DAQ system that converts the six amplified voltages from the amplifier into digital values.

Computer (user-supplied) A computer to use the digital values from the DAQ system.

Software (user-supplied)Software that uses the data provided by the TWE Calibration Spreadsheet and the digital values from the DAQ system to convert the values into the transducer’s F/T loads.

TWE Calibration Spreadsheet

The ATI Calibration Spreadsheet with the correct FTxxxxx serial number, after the user has input the system characterization data (refer to Section 3.2.3—Worksheet 3. System Characterization).

Cables and Connectors (user-supplied)

Cables and connectors for the following:

• to connect the transducer to amplifier inputs and excitation voltage supply

• to connect the amplifier outputs to the inputs of a DAQ system

• to connect the DAQ system to a computer

Signals in a TWE system are detailed in the following table:

Table 3.2—Signals in a TWE SystemSignal Name Source: Used By: Description

Excitation Voltage User Excitation Supply ATI Transducer

A voltage supply that powers the transducer. It should have low noise and low drift.

Low-level Voltages Transducer User’s AmplifiersSix outputs (g0, g1, g2, g3, g4, and g5) of the ATI transducer before amplification.

Amplified Voltages User’s Amplifiers User’s DAQ system Six amplified outputs (G0, G1, G2, G3, G4, and G5) of the user’s amplifiers.

Digitized Voltages User’s DAQ System User’s Computer

Digital representation of the six amplified outputs (G0, G1, G2, G3, G4, and G5).




3.1 Excitation Voltage Supply and Six AmplifiersThe excitation voltage supply and the six amplifiers are grouped together in this section because these functions are commonly put on the same circuit board or are found in the same off-the shelf equipment. A graph in Appendix B—Amplification and Excitation shows the relationship between amplification, excitation, and output range.

3.1.1 Excitation Voltage SupplyThe customer-supplied excitation voltage supply (Vexc) provides power to the transducer. The signals output by the transducer are directly proportional to the excitation voltage supply and the applied load. Because these signals are directly proportional to the excitation voltage supply, it is critical that the supply has both low noise and low drift.

The recommended values and specifications for excitation voltage supply (Vexc) are in the following tables:

Table 3.3—Recommended Values for Excitation Voltage Supply (Vexc)

Parameter Value Notes

Vexc 5 VDC Lower voltages increase thermal stability but may lower signal to noise ratio.

Table 3.4—Excitation Voltage Supply (Vexc) Specifications

ParameterValue

NotesMinimum Maximum

Vexc N/A 10 VDC Thermal drift increases as output voltage increases.

Transducer Input

Resistance

Gamma Transducer 275 Ω

N/A

The excitation voltage supply must be able to provide current to a resistive load at this amount or lower.

Other Transducers 500 Ω

Output noise on the excitation voltage supply is notated as Vexc_noise. For each transducer gage signal the output the Vexc_noise is halved and amplified with the strain gage signals. The noise passed to the unamplified transducer gage signal in mV/V form equals:

Output drift on the excitation voltage supply is notated as Vexc_drift. For each transducer gage signal the output the Vexc_drift is halved and amplified with the strain gage signals. The noise passed to the unamplified transducer gage signal in mV/V form equals:

Use an excitation voltage supply based on a precision voltage reference. Precision voltage reference integrated circuits (ICs) can have excellent noise and drift characteristics and perform much better than laboratory power supplies. Precision voltage reference evaluation boards are available from many electronics distributors and manufacturers of precision voltage references. A web search for “precision voltage reference evaluation board” will help locate information about such boards.




The amount of excitation voltage supply noise it takes to create one bit of noise on the DAQ system is shown in the following graph. This graph does not account for noise added during amplification, noise coupled from external sources, or mechanical noise sensed by the transducer. Four excitation voltages are shown in the graph: 2.5 V, 3.3 V, 5 V, and 10 V. A DAQ system analog-to-digital converter (ADC) resolutions of 10 bits through 24 bits are shown in the graph,for example: a system with a 3.3 V excitation and a 16-bit ADC creates one bit of noise, if Vexc_noise exceeds 1x10-4 V (100 μV).

Figure 3.1—Vexc_noise Resulting in One ADC Bit of Noise

1E-7 V

1E-6 V

1E-5 V

1E-4 V

1E-3 V

1E-2 V

1E-1 V

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Vexc_noise

Total ADC Bits

2.5 V3.3 V5 V10 V

Vexc

3.1.2 Six AmplifiersThe TWE transducer’s outputs need to be amplified to work with a user’s DAQ system. Each of the TWE transducer’s six outputs require a user-supplied amplifier. The amplifiers perform the following functions:• to increase the transducer’s low-level outputs to a range appropriate for the DAQ system

• to remove any offset from the transducer’s signalsWhile fixed-gain amplifiers may be used, variable-gain amplifiers are preferred because they can be adjusted to more closely match the ideal gain. Closely matching the ideal gains helps ensure the system provides the best combination of resolution and range. Gains that are too high result in coarser resolution, while gains that are too low result in limited range.The ideal gain for each amplifier can be calculated by the TWE Calibration Spreadsheet (TWE FTxxxxx.xlsx). The ideal gain amplifies the transducer’s outputs to best fit the DAQ systems inputs. This matching ensures the full loading range of the transducer can be read at the highest resolution. Appendix B—Amplification and Excitation has a graph that shows the relationship between amplification, excitation voltage, and transducer signal output range.To ensure the full loading range can be read, the amplifiers need to trim any offset from the transducer signals.

The nominal unloaded output of each half bridge is a voltage halfway between Vexc- (lower excitation voltage) and Vexc+ (upper excitation voltage), expressed mathematically as:




All strain gage output voltages have some offset bias voltage present. This offset bias voltage is the shift of the strain gage output from ideal unloaded output (gnom). Removing this offset voltage, prior to amplifying the signals, allows user-supplied equipment to operate at the most sensitive measurement range. The most effective way to remove offset voltage is to use a differential amplifier with a fixed bias reference voltage identical to this offset voltage. This bias reference voltage serves as the amplifier’s negative voltage input, while the strain gage voltage is the positive.An easy way to generate this bias reference voltage for each strain gage is with a single 10-turn 200 Ω potentiometer and two 1000 Ω resistors (see Figure 3.2). Adjust the reference output voltage without anything mounted to the transducer. Place it on a level surface. Adjust the potentiometers so the DAQ output reads midrange.

Figure 3.2—Example Bias Reference Voltage Circuit (user-supplied)

3.1.3 DAQ SystemThe user-supplied DAQ system converts the six amplified strain gage signals from voltages to digital values for a computer to process.

3.1.4 ComputerThe user-supplied computer reads the digital values from the DAQ system. These values can be entered into the TWE Calibration Spreadsheet (refer to Section 3.2—TWE Calibration Spreadsheet (FTxxxxx TWE.xlsx)).

3.1.5 Connections (cables and connectors)Users must electrically connect their supplied amplifiers and excitation to the transducer. For information on the connections from the transducer, refer to Appendix A—Transducer Cable Connectors and Signals. Install the DAQ system software on the computer. Connect the DAQ system to the computer. Connect the DAQ system inputs to the outputs of the amplifiers.

3.2 TWE Calibration Spreadsheet (FTxxxxx TWE.xlsx)For a general overview of the spreadsheet, refer to Section 2.5—TWE Calibration Spreadsheet Overview. A more detailed description of each worksheet and instructions to use the spreadsheet are in the following sections. In the spreadsheet, the first four of the worksheets are numbered in the order that they should be used. The last worksheet (Gain Worksheet) is not required for users to operate their system. This worksheet is intended as an optional help-aid to assist users as they measure their amplifiers’ gain.Most cells in the spreadsheet should not be modified. The cells for entering data are shaded. The five worksheets in the spreadsheet are described in the following sections.

NOTICE: Depending on the transducer, the worksheets may vary slightly in appearance from the following example figures of each worksheet, but the worksheet functionality is the same.




3.2.1 Worksheet 1. OverviewThe 1. Overview worksheet provides a summary for each of the five worksheets in the spreadsheet and brief instructions for how the each worksheet should be used.

Figure 3.3—Screen Capture of Worksheet 1. Overview




3.2.2 Worksheet 2. Electrical SetupThe 2. Electrical Setup worksheet guides the user through building a TWE system. The Electrical Overview schematic shows the necessary components for a TWE system and describes how signals pass from one component to another.The Building the Transducer System section contains a setup procedure for connecting the system components. After a task is completed, select the corresponding check box. In the following image, the user has checked boxes as steps were completed.

Figure 3.4—Screen Capture of Worksheet 2. Electrical Setup




3.2.3 Worksheet 3. System CharacterizationIn this worksheet (Figure 3.5), the user inputs values for various characteristics of their TWE system. These values are used to develop the Amplified Calibration Matrix that is used to convert digitalized voltages into usable F/T values.In the Overview section schematic, the numbered call outs point to system components. These call outs reference to a step in the Instructions section of the worksheet. These steps require the TWE system is electrically connected and operating. For step four, the user needs measure the user-supplied amplifier gains and type these values in the worksheet. For this step, temporarily disconnect the TWE transducer from the amplifies, and then apply voltages to the amplifier inputs. Use a voltmeter to measure the values. Record the readings in the Gain Worksheet (refer to Section 3.2.5—Worksheet Gain Worksheet). The Gain Worksheet can assist the user to calculate the amplifier gains for step four in the 3. System Characterization worksheet.




Figure 3.5—Screen Capture of Worksheet 3. System Characterization




3.2.4 Worksheet 4. Sample CalculationsThis worksheet performs the conversion of the DAQ system’s amplified strain gage voltages into resolved F/T data. Formulas for the calculations are provided on the worksheet. Users can use these formulas to aid them as they create their own software to complete F/T calculations.

Figure 3.6—Screen Capture of Worksheet 4. Sample Calculations




3.2.5 Worksheet Gain WorksheetThe Gain Worksheet steps the user through the process of measuring the gains of their amplifiers. This worksheet is intended as a helpful resource and not required to be used.The user applies a series of test voltages to the input of an amplifier while measuring the test voltages and the amplifier outputs. The worksheet suggests three test voltages to use. These test voltages are based on the values input to the worksheet Worksheet 3. System Characterization. In the provided table, the user records the actual test voltages used and the amplifier output voltages. Note that the user can change the Units column of the table to either mV or V, as appropriate for the measurements.The calculated gains are in the Measured Gain Results section. These values should be copied and pasted as values into step four of worksheet 3. System Characterization (refer to Section 3.2.3—Worksheet 3. System Characterization).

Figure 3.7—Screen Capture of Gain Worksheet




3.3 How to Use the TWE Calibration SpreadsheetAn overview of the TWE calibration spreadsheet is in Section 2.5—TWE Calibration Spreadsheet Overview.To ensure the transducer is used over its entire calibration range with maximum resolution, use the spreadsheet per the following instructions.

1. Electrically connect the transducer to the user-supplied excitation voltage, amplifiers, and DAQ system as outlined in the worksheet Worksheet 2. Electrical Setup.

2. Input the values of the system into the Worksheet 3. System Characterization.a. In the 3. System Characterization worksheet, type the high and low excitation voltages of the

system. For information regarding the excited voltage supply, refer to Section 3.1.1—Excitation Voltage Supply.

b. Next, type the maximum and minimum desired output of the system. If using a DAQ system, the desired output range is determined by the input range of the DAQ. For example: a DAQ with a ±5 V input range would use 5 V for the maximum input voltage and -5 V for the minimum input voltage.

NOTICE: The worksheet uses the information from step b to provide optimum target gain settings for each gage. This amplification allows the transducer to be used over its entire calibration range with maximum resolution.

c. Adjust the amplifiers to provide gains approximately equal to the values from step b (for general information about amplification, refer to Section 3.1.2—Six Amplifiers).

d. Measure the actual gains of each strain gage channel in the circuit and enter them into the worksheet.

e. Adjust the hardware bias circuity so the amplified outputs are midrange when the unmounted transducer is placed MAP side down on a level surface. Making this adjustment ensures the transducer’s full range is available. For general information about bias circuitry, refer to Section 3.1.2—Six Amplifiers.

3. Use the workbook Worksheet 4. Sample Calculations to test the complete system’s operation. a. With the transducer at rest, take a measurement of all six strain gage channels.

b. Type these values into the reference measurement cells in the Worksheet 4. Sample Calculations.

c. Place a known load on the transducer, and type this measurement value into the loaded measurement cells. NOTICE: The easiest scenario for taking this test load is to place a weight on the Z axis. If the mass is centered on the Z axis, there will be little Tx and Ty readings. For this test, ATI suggests using a weight that applies at least one quarter of the transducer’s Fz sensing range.

d. Verify that the resolved loads calculated by the spreadsheet match the expected results.

4. Incorporate the formulas from the Worksheet 4. Sample Calculations page and the Amplified Calibration Matrix from the Worksheet 3. System Characterization into the final application.

CAUTION: Before performing the F/T conversion, every voltage measurement should be checked for saturation of the A/D converter. If one or more of the six gage channels is saturated, F/T values cannot be accurately calculated and the transducer may be in danger of damage due to excessive loading.




4. Periodic MaintenanceTo keep the transducer functioning at peak performance, incorporate the following maintenance items on an annual basis.

4.1 Inspection of CablesFor most applications there are no parts that need to be replaced during normal operation. With industrial-type applications that continuously or frequently move the system’s cabling, you should periodically check the cable jacket for signs of wear.The transducer must be kept free of excessive dust, debris, or moisture. The internal structure of the transducer can become clogged with particles and will become uncalibrated or even damaged. For example, in applications with metallic debris such as electrically-conductive material, protect the transducer from debris by keeping the transducer enclosed in a resistant housing. Non-IP rated sensor are considered to have no ingress protection.

4.2 CalibrationPeriodic calibration of the transducer is required to maintain traceability to national standards. Follow any applicable ISO-9000-type standards for calibration. ATI Industrial Automation recommends annual recalibrations, especially for applications that frequently cycle the loads applied to the transducer.




5. TroubleshootingCustomer service is available for problems or questions not addressed in the manuals.

Note

Please read the manual before calling customer service. Before calling, have the following information available:

1. Serial number (e.g., FT01234)

2. Transducer model (e.g., Nano17, Gamma, Theta, etc.)

3. Calibration (e.g., US-15-50, SI-65-6, etc.)

4. Accurate and complete description of the question or problem

5. Computer and software information. Operating system, computer type, drivers, application software, and other relevant information about your configuration.

If possible, be near the F/T system when calling.

Please contact an ATI representative for assistance, if needed:ATI Industrial Automation 1031 Goodworth Drive Apex, NC 27539 USA www.ati-ia.com

Application Engineering Tel: +1.919.772.0115, Extension 511 Fax: +1.919.772.8259 E-mail: [email protected]



mailto:ft_support%40ati-ia.com?subject=



6. AppendixInformation in these appendixes aid the user during initial setup of the TWE system.

6.1 Appendix A—Transducer Cable Connectors and Signals6.1.1 Transducer Mating Connectors

The connector styles for each transducer type are listed in the following table:

Table 6.1—Transducer Mating ConnectorsTransducer

TypeATI Transducer

ExampleConnector

Style Manufacturer Manufacturer P/N

9105-TWEnon-IP rated

Gamma, Delta, and Omega

cable mount Hirose HR25-9TP-205(73)

9105-TWLIP-rated Gamma,

Delta, and Omega sensors.

cable mount Lemo FGG.3K.320.CLA

9105-TW Nano and Minicable mount Amphenol T-3636-001

chassis mount Amphenol T-3638-009

6.1.2 Pin Connections on the Cable Connectors

CAUTION: Although the cables used by ATI Industrial Automation are robust, the individual wires in the cables must be handled with care to avoid damaging them. Correctly-sized wire strippers are required and the wires must be strain relieved and anchored where ever they are soldered to prevent breaking.

6.1.2.1 Nano/Mini Integral Cable ConnectorsConnector pin numbers with their corresponding signal description are listed in the following table:

Table 6.2—Wiring for Nano/Mini Integral CablesSchematic of the

Connector Pin Out (pin side of transducer connector)

Pin Wire Color Description

A --- No connectionB Yellow g4 outputC Brown g5 outputD Violet g2 outputE Blue g3 outputF Green g0 outputG Orange g1 outputH --- No connectionJ Black Vexc- excitation inputK Red Vexc+ excitation input




6.1.2.2 9105-C-x-A Cable ConnectorsConnector pin numbers with their corresponding signals are listed in the following table

Table 6.3—Connector Connections in 9105-C-x1-A CablesPin Number for Connector:

Wire Color SignalH2 L3 A4

6 1 K Red Vexc+

10 4 J Black Vexc-

1 7 F Brown g07 9 G Yellow g1

17 11 D Green g28 13 E Blue g3

13 15 B Violet g49 17 C Grey g52 5

Not Connected

Orange

N/A

3 8 Brown/White4 14 Blue/White5 18 Grey/White11 2 Red/White12 10 Yellow/White14 19 White15 3 Black/White16 6 Orange/White18 16 Violet/White19 20 White/Black20 12 Green/White

Notes:1. In the part number 9105-C-x-A, x is either H or L for the transducer end of the cable), and A

for the electronics end of the cable.2. Column H applies to the 9105-TWE transducers.3. Column L applies to the 9105-TWL transducers.4. Column A applies to the 9105-TW transducers. The cable part number for TW transducers

is 9105-C-X-A.




6.2 Appendix B—Amplification and ExcitationFigure 6.1 shows how much amplification is needed to achieve a given output range for a given excitation voltage and transducer sensitivity. The chart in the following figure shows the gain calculations made by the spreadsheet FTxxxxx TWE.xlsx (refer to Section 3.2—TWE Calibration Spreadsheet (FTxxxxx TWE.xlsx)). Output ranges can be bipolar (± x V, on the left axis) or unipolar (0 V to x V, on the right axis). The required amplification for a 5 V excitation is shown on the top axis. The bottom axis is the product of amplification and the excitation voltage.To use the Figure 6.1:

1. Determine the required output type, either bipolar or unipolar. This is usually determined by the input range of the DAQ used to read the amplifier outputs.

2. Determine the required output range in volts. This is usually determined by the input range of the DAQ used to read the amplifier outputs.

3. Determine the excitation voltage that supplies the transducer.4. Determine the transducer signal output range in mV/V. This can be found in the FTxxxxx TWE.

xlsx spreadsheet, Worksheet 3. System Characterization, in the Supplemental Information section (Figure 3.5), Transducer Low-level Voltage Output Ranges table, row In mV/V form.

NOTICE: If the excitation voltage is 5 V, then use the top axis to determine the amount of amplification needed. If the excitation voltage is not 5 V, then use the bottom axis. In that case, divide the values on the bottom axis by the excitation voltage to get the amplification.

5. Plot a line for the transducer signal output range on the graph. Find where the selected output range on the appropriate vertical axis crosses the plotted line for the transducer signal output range. Follow this point to the appropriate horizontal axis. This will show the amount of gain needed.

6.2.1 ExamplesThe following examples demonstrate how to use the graph (Figure 6.1) to find the amount of gain needed.Example One:The DAQ input range is unipolar, ranging from 0 V to 20 V. The excitation voltage is 5 V. The transducer signal output range of the strain gage of interest is 55 mv/V.Use the right vertical axis because the DAQ input range is unipolar. Use the top horizontal axis because the excitation voltage is 5 V. The 20 V level of the left vertical axis intersects the 55 mV/V line at 72.7 on the top horizontal axis. The required amplification is 72.7. Example Two:The DAQ input range is bipolar, ranging from -10 V to + 10 V (±10 V). The excitation voltage is 4 V. The transducer signal output range of the strain gage of interest is 15 mV/V.Use the left vertical axis because the DAQ input range is unipolar. Use the bottom horizontal axis because the excitation voltage is not 5 V. The ±10 V level of the left vertical axis intersects the 15 mV/V line at 666.7 V on the bottom horizontal axis. Divide the 666.7 V by the 4 V excitation to get 166.7. The required amplification is 166.7.




Figure 6.1—Amplification vs. Output Range for Various Sensitivities

5 m

V/V

Av×

Exc.

=666

.7 V

15 m

V/V

25 m

V/V

35 m

V/V

45 m

V/V

10 m

V/V

7.5

mV/

V

20 m

V/V

Av=

72.7

55 m

V/V

0 V

10 V

20 V

30 V

40 V

±0 V

±5 V

±10

V

±15

V

±20

V

Am

plifi

catio

n (A

v) fo

r 5 V

Exc

itatio

n

Uni

pola

r O

utpu

t Ran

geB

ipol

ar

Out

put R

ange

Am

plifi

catio

n (A

v) ×

Exci

tatio

n

3500

/ V

3000

/ V

2500

/ V

2000

/ V

1500

/ V

1000

/ V

500 /

V

0 / V0

100

200

300

400

500




6.3 Appendix C—Mechanical and Electrical Overview of the TransducerAn overview of the transducer requires a brief mechanical and electrical summary of the design. Mechanical principles define the movement of the transducer. Based on these mechanical principles, ATI integrates electronics into the transducer to measure its physical movements. These electronics relay signals that report F/T data to the user’s system.

6.3.1 Mechanical DescriptionThe transducer reacts to applied forces and torques using Newton’s third law of motion: to every action there is always opposed an equal reaction; or, the mutual action of two bodies upon each other are always equal, and directed to contrary parts.

Figure 6.2—Applied force and torque vector on transducer

Force and torque are three-dimensional vectors, which can be broken into three orthogonal components.The force applied to the transducer flexes three symmetrically placed beams using Hooke’s law: σ = Ε · εwhere:

σ = stress applied to the beam (σ is proportional to force)

Ε = elasticity modulus of the beam

ε = strain applied to the beam

NOTICE: The transducer is a monolithic structure. The beams are machined from a solid piece of metal. This decreases hysteresis and increases the strength and repeatability of the structure.




Silicon semiconductor strain gages are attached to the beams and function as strain-sensitive resistors. The resistance of the strain gage changes as a function of the applied strain: ∆R = Sa · Ro · εwhere:

∆R = Change in resistance of strain gage

Sa = Gage factor of strain gage

Ro = Resistance of strain gage unstrained

ε = Strain applied to strain gage

The output voltages from the transducer’s gages are used to measure the change in resistance. They must be combined mathematically to be converted into forces and torques (refer to Section 3.2—TWE Calibration Spreadsheet (FTxxxxx TWE.xlsx)).

6.3.2 Electrical DescriptionThe transducer is instrumented with high-quality silicon semiconductor strain gages. The high output of these silicon strain gages requires far less amplification than foil-based strain gages. The higher amplification required by foil strain gages boosts their signals and any noise present. Since silicon strain gages require less amplification there is less noise amplification. Silicon strain gages also allow transducers to survive higher overload conditions without damage. The transducer uses six half-bridge strain gage pairs to sense loads. For all transducers except the Gamma, the excitation power supply (Vexc+, Vexc-) must supply a 500 Ω load. The Gamma requires the ability to supply a 275 Ω load. Figure 6.3 shows the electrical equivalent schematic of the transducer. Each half-bridge strain gage pair measures a portion of the total transducer load. A load places compressive strain on one member of the gage pair and equally tensile strain on the other member. The pair works together as a voltage divider to produce a signal representing the pair’s load.

Figure 6.3—Transducer Equivalent Schematic




6.4 Appendix D—ResolutionATI’s transducers have a three sensing beam configuration, where the three beams are equally spaced around a central hub and attached to the outside wall of the transducer. This design transfers applied loads to multiple sensing beams and allows the transducer to increase its sensing range in a given axis if a counterpart axis has reduced loading (for compound loading information, refer to the F/T Transducer manual).The resolution of each transducer axis depends on how the applied load is spread among the sensing beams. The best resolution occurs in a scenario when the quantization of the gages is evenly distributed as load is applied. In the worst case scenario, the discrete value of all involved gages increases at the same time. The typical scenario will be somewhere in between the two aforementioned scenarios.F/T resolutions are specified as typical resolution, defined as the average of the worst and best case scenarios. Because both multi-gage effects can be modeled as a normal distribution, this value represents the most commonly perceived, average resolution. The DAQ F/T resolutions are based on real-number calculations and do not result in clean fractions. To express the values as clean fractions, use the best values achieved by a 16-bit data acquisition system. Although this misrepresents the actual performance of the transducers, it results in a close (and always conservative) estimate.

6.5 Appendix E—Detecting Sensitivity ChangesSensitivity checking of the transducer can also be used to measure the transducer system’s health. This can be done by applying known loads to the transducer and verifying the system output matches the known loads.For example, for a transducer with an end-effector attached:

1. If the end-effector has moving parts, they must be moved in a known position.2. Place the transducer in an orientation that allows the gravity load from the end-effector to exert load on

many transducer output axes.3. Record the output readings.4. Position the transducer to apply another load, this time causing the outputs to move far from the

earlier readings.5. Record the second set of output readings.6. Find the differences from the first and second set of readings and use it as your sensitivity value.Even if the values vary somewhat from sample set to sample set, they can be used to detect gross errors. Either the resolved outputs or the raw transducer voltages may be used (the same must be used for all steps of this process.

6.6 Appendix F—Buffer CircuitIf a data acquisition system has an input impedance of 5 kΩ or less, implement an amplifier circuit or a simple follower to provide a high-impedance output. If designing a simple voltage follower, then enter a gain of 1 into the TWE calibration spreadsheet. Otherwise, measure the gain and offset of the circuit. The gain is the ratio of Δ output ÷ Δ input.




7. Terms and Conditions of SaleThe following Terms and Conditions are a supplement to and include a portion of ATI’s Standard Terms and Conditions, which are on file at ATI and available upon request.

ATI warrants to Purchaser that force torque sensor products purchased hereunder will be free from defects in material and workmanship under normal use for a period of one (1) year from the date of shipment. The warranty period for repairs made under a RMA shall be for the duration of the original warranty, or ninety (90) days from the date of repaired product shipment, whichever is longer. ATI will have no liability under this warranty unless: (a) ATI is given written notice of the claimed defect and a description thereof with thirty (30) days after Purchaser discovers the defect and in any event, not later than the last day of the warranty period and (b) the defective item is received by ATI not later than (10) days after the last day of the warranty period. ATI’s entire liability and Purchaser’s sole remedy under this warranty is limited to repair or replacement, at ATI’s election, of the defective part or item or, at ATI’s election, refund of the price paid for the item. The foregoing warranty does not apply to any defect or failure resulting from improper installation, operation, maintenance, or repair by anyone other than ATI.

ATI will in no event be liable for incidental, consequential, or special damages of any kind, even if ATI has been advised of the possibility of such damages. ATI’s aggregate liability will in no event exceed the amount paid by the purchaser for the item which is the subject of claim or dispute. ATI will have no liability of any kind for failure of any equipment or other items not supplied by ATI.

No action against ATI, regardless of form, arising out of or in any way connected with products or services supplied hereunder, may be brought more than one year after the cause of action accrued.

No representation or agreement varying or extending the warranty and limitation of remedy provisions contained herein is authorized by ATI, and may not be relied upon as having been authorized by ATI, unless in writing and signed by an executive officer of ATI.

Unless otherwise agreed in writing by ATI, all designs, drawings, data, inventions, software, and other technology made or developed by ATI in the course of providing products and services hereunder, and all rights therein under any patent, copyright, or other law protecting intellectual property, shall be and remain ATI’s property. The sale of products or services hereunder does not convey any expressed or implied license under any patent, copyright, or other intellectual property right owned or controlled by ATI, whether relating to the products sold or any other matter, except for the license expressly granted below.

In the course of supplying products and services hereunder, ATI may provide or disclose to Purchaser confidential and proprietary information of ATI relating to the design, operation, or other aspects of ATI’s products. As between ATI and Purchaser, ownership of such information, including without limitation any computer software provided to Purchaser by ATI, shall remain in ATI and such information is licensed to Purchaser only for Purchaser’s use in operating the products supplied by ATI hereunder in Purchaser’s internal business operations.

Without ATI’s prior written permission, Purchaser will not use such information for any other purpose of provide or otherwise make such information available to any third party. Purchaser agrees to take all reasonable precautions to prevent any unauthorized use or disclosure of such information.

Purchaser will not be liable hereunder with respect to disclosure or use of information which: (a) is in the public domain when received from ATI, (b) is thereafter published or otherwise enters the public domain through no fault of Purchaser, (c) is in Purchaser’s possession prior to receipt from ATI, (d) is lawfully obtained by Purchaser from a third party entitled to disclose it, or (f) is required to be disclosed by judicial order or other governmental authority, provided that, with respect to such to maintain the confidentiality of such information.


Documents

F/T Transducer Without Electronics (TWE) ManualEngineered Products for Robotic Productivity Pinnacle Park • 1031 Goodworth Drive • Apex, NC 27539 • Tel: +1-919.772.0115 • Fax: